This invention has as its object the provision of a liquid cooler which is particularly suitable for the cooling of semiconductor power elements.
Up to now liquid coolers have been used rather seldom for the cooling of semiconductor power elements because cooling semiconductor power elements with relatively low power losses by air has been substantially simpler. However, with increasing heat losses of such semiconductor power elements, the dimensions of air coolers has increased so that now cooling arrangements employing air as the cooling medium are very much larger than arrangements employing a liquid as the cooling medium.
Designers of cooling arrangements for semiconductor power elements are now starting to use liquids as the cooling medium, since liquid cooling media have a much higher heat absorbing capacity than air, and in addition, meet with safety requirements as to shock and transient conditions because their heat inertia can absorb short heat impulses with only a small increase in temperature.
Liquid cooling also substantially reduces the noise level which inherently accompanies air cooled arrangements, since with liquid cooling it is possible to reduce or even completely to eliminate noise by disposing the heat exchanger and the necessary pumps outside the space in which the semiconductor power element is located. These advantages, however, are somewhat reduced by the complexity of cooling systems which employ liquid cooling media and the requirement for their maintenance, both of which result in increased operating costs. Despite such complications liquid cooling with forced circulation of the cooling medium holds out much promise for the cooling of semiconductor power elements.
Known liquid coolers are usually designed with straight liquid conducting channels, mainly because of their simple manufacturing technology. Such coolers are usually formed of material having good heat conductivity, such as for example copper. However, laminar layers are formed on the walls of such straight channels, thereby reducing the heat transfer from the body of the cooler to the cooling medium. There are also known arrangements of liquid coolers (U.S. Pat. No. 3,823,771) wherein a circular plate with radial grooves is fitted on at least one said thereof to a flat connecting piece provided with concentric circular grooves for the supply of cooling liquid. These arrangements are simple from the technological viewpoint; however, because of insufficient turbulence of the cooling liquid during its passage through the cooler they do not provide the required cooling effect for the space which is provided for the cooler in certain applications.